This invention relates generally to fibers, and more particularly relates to fiber-based microelectronic devices.
The field of wearable electronics has recently received substantial attention as a possible platform for connection between humans and flexible electronic devices. So-called ‘wearable’ devices are now available, but are separate and distinct from wearable fabric because the devices cannot be incorporated into a fabric production process, generally due to the non-fiber form of the devices. Yet fibers and yarns are the main building blocks of textiles.
Optical fiber is the main building block of modern communication systems. There has been demonstrated the ability to produce multifunctional optical fibers by combining different sets of materials to achieve corresponding fiber functions. Additionally, here has been demonstrated the use of optical fiber as a platform for supporting external devices, e.g., as a carrier for microelectronic devices that are positioned on the surface of the fiber.
The thermal drawing of optical fiber is a powerful and well established process that enables the production of a wide range of fiber geometries. But thermal drawing imposes limits on the functionality of the drawn fiber. For example, the set of materials that can be thermally drawn into a fiber is limited by the thermomechanical properties of the materials. Conventionally, in order to achieve a successful fiber draw, all fiber materials to be co-drawn must flow at the same temperature, requiring the materials to have similar viscosities while maintaining chemical compatibility with each other at the draw temperature. As the draw temperature is lowered, the set of materials that can be integrated into the fiber is increasingly limited. As the draw temperature is increased, diffusion and mixing of and undesired chemical reaction between drawn materials increases, often prohibiting the use of materials that are required to achieve desired fiber structure and/or functionality.
The materials employed in conventional, commercial microelectronic devices are not in general compatible for co-drawing into fiber form because such devices require a large set of materials, including crystalline semiconductors, high melting temperature alloys, thin films, and thermoset polymers, and these in general are not compatible for co-drawing. For example, light emitting diodes typically include at least two doped semiconductor materials as well as metallization materials, which are not in general compatible for thermal co-drawing. As a result of these material limitations, as well as fabrication requirements for micro-scale dimensional control imposed by microelectronic devices, the full integration of devices, such as microelectronic devices, into fiber-based textiles has not historically been achievable.